1. Field of the Invention
The present invention relates to a brushless motor and a manufacturing method thereof.
2. Description of Related Art
In a previously known type of brushless motor, a rotor is rotatably supported relative to a motor shaft through two ball bearings (see, for example, Japanese Unexamined Patent Publication No. H08-047199). Japanese Unexamined Patent Publication No. H08-047199 discloses a spindle motor. In the case of Japanese Unexamined Patent Publication No. H08-047199, a generally cylindrical bearing holder is formed in a rotor, and two ball bearings are received in an interior of the bearing holder such that the ball bearings are spaced from each other in an axial direction of a stationary shaft. The rotor is supported by the ball bearings in a rotatable manner relative the stationary shaft, which is held by a bracket.
However, in the case of Japanese Unexamined Patent Publication No. H08-047199, the bearing holder is placed radially inward of the stator, around which windings (acting as heating elements) are wound. Thus, the heat from the stator can be easily conducted to the ball bearings, which are received in the interior of the bearing holder. Thereby, the bearings need to be highly heat resistant, so that costs of the brushless motor are disadvantageously increased.
Furthermore, in the case of Japanese Unexamined Patent Publication No. H08-047199, two large diameter portions (increased diameter portions) are provided at two axially opposed ends, respectively, of an inner bore of the bearing holder to hold the ball bearings, respectively. Thus, in order to install the ball bearings in the same common direction, the rotor needs to be inverted after installation of one of the ball bearings into the bearing holders prior to installation of the other one of the ball bearings into the bearing holder. Therefore, the work efficiency is reduced, and the costs are increased.